Field of the Invention
This invention relates to an adjustable length strut for laterally supporting one or both of the lower steering arms of a three point linkage of an agricultural tractor, the linkage being utilised to attach an agricultural implement to the tractor. Such a strut comprises an outer member, or sleeve, and an inner member telescopically engaged with one another wherein the two members are lockable relative to one another in certain positions by means of spaced bores provided therein which are capable of being aligned relative to one another for locking by a pin inserted into the aligned bores. One of the members is connectable to the tractor and the other of such members is connectable to a said lower steering arm.
With known struts of this type, the inner and outer members are provided with axially spaced bores through which the locking pin may be inserted but, in such designs, all of the bores extend through the members in a common plane, e.g. a vertical plane, which also passes through the longitudinal axis of the strut. The bores in the outer member are equidistantly axially spaced apart longitudinally thereof as are the bores in the inner member but the axial distances between adjacent bores in the outer member are different to the corresponding distances between the bores in the inner member. This arrangement permits a large number of lockable positions wherein sets of bores in the outer and inner members re alignable with one another thus providing a vernier type of adjustment as between the inner and outer members.
Although the type of adjustable length strut described above permits a large number of adjustments in length, it is left to the user i.e. the farmer to find the correct position which has to be set. As a rule, only a relatively small number of positions are required for coupling the lower steering arms to the corresponding implement which means that the user has to find the correct adjustment position for the struts by trial and error. However, if the incorrect length of strut is set, it is possible that the lower steering arms may run up against their stops when the associated lifting device is actuated thus leading to possible damage. It will be appreciated that the object of providing lateral struts is to set a predetermined horizontal distance between the ends of the lower steering arms for the purposes of coupling them to the implement but, in addition, the struts are also intended to limit the lateral deflection of the implement and to permit adjustment of the implement relative to the direction of traction.